<p>Two-dimensional (2D) nanomaterials, such as graphene, transition metal dichalcogenides (TMDs), MXenes, and their heterostructures, are shaping the future of sensing technology. Their extremely high surface-to-volume ratio, tunable electronic structure, and versatile surface chemistry provide high sensitivity and selectivity for detecting biological and environmental analytes. This study discusses current advances in the design and deployment of 2D nanomaterial-based sensors, with a particular emphasis on biosensing and environmental monitoring. Key detection strategies—including electrochemical, optical, and field-effect transistor (FET) platforms—are rigorously examined. Practical applications are emphasized, including rapid biomarker testing, wearable healthcare devices, air quality assessment, and water contamination monitoring. Integration with imaging techniques, artificial intelligence (AI), and Internet of Things (IoT) systems is proposed as a pathway toward smart durable sensor technologies. Finally, the challenges of scalability, repeatability, and operational stability are evaluated. Future research directions are also proposed to accelerate the transfer of 2D nanomaterial-based sensors from laboratory prototypes to real-world applications.</p>